MAXI News

On-demand data archive is now open to public

Tatehiro Mihara — Tue, 08 Nov 2011 07:54:10 +0000

On-demand data of MAXI/GSC is available. You can get spectrum of any sky position of any time. Please visit

http://maxi.riken.jp/mxondem

There is also a short-cut “on-demand data” on the maxi-riken top page (http://maxi.riken.jp/top), or you can select “Data Products” tab and click “go to on-demand page”.

The data are limited to those taken with 1650-V counters since 2009 October 31 to 2 days ago excepting for the GSC_3. Please read the notes in “About this page” before you start the analysis.

MAXI detection of a super-burst from EXO 1745-248 in Terzan 5

Tatehiro Mihara — Tue, 01 Nov 2011 10:06:35 +0000

We analyzed the MAXI/GSC light curve of an X-ray burst from EXO
1745-248 in Terzan 5 reported in Atel #3714, #3718, #3720 and found
that the initial peak at MJD 55858.53 decayed exponential with an
e-folding time of 10 hour.
If the emission is a blackbody radiation, the temperature can be estimated from the hardness of two energy bands.

MJD      4-10/2-4 keV   kT [keV]      10-20/4-10 keV   kT [keV]
55858.53      2.9         2.9 +- 0.8       0.32    2.4 +- 0.6
55858.59      1.5         1.7 +- 0.4       0.19    2.0 +- 0.8
55858.78      1.05        1.4 +- 0.4       0.50    2.8 +- 1.0
55858.84      1.24        1.58 +- 0.5       0.37 1.85 +- 0.8
55858.91      1.06        1.43 +- 0.5       0.19 1.83 +- 1.5
55858.97      1.03       1.40 +- 0.5        0.06 1.80 +- 3.9
(Errors are 1-sigma.)

The values derived from 4-10/2-4 keV and 10-20/4-10 keV
are consistent with each other. It showed a softening from 2.9 keV in the beginning to 1.5 keV in the end.

The fluence is 2.4 x 10⁴² erg in 2-10 keV assuming 8.7 kpc distance (Cohn et al. ApJ 571 818 (2002)). Using H burning energy of 6 x 10¹⁸ erg/g, the mass of H is 4.0 x 10²³ g. Using the average flux of 10 mCrab (1.7 x 10³⁶ erg/s, 9.0 x 10¹⁵ g/s), the reputation time is calculated to be 510 yr. (<- It was a mistale. Correctly 510 days. If we use C-burning energy it becomes 5100 days = 14 yrs. by TM 2011.11.16)

The sphere radius of the blackbody is 6.3 km with using 2 keV and 6.8 x 10³⁷ erg/s at the peak.

These results (e-folding time, temperature, softening, fluence, and radius) are typical as a super-burst from low-mass X-ray binaries.

Atel #3729

Archived light-curve data is available at

http://maxi.riken.jp/top/index.php?cid=1&jname=J1748-248

MAXI/GSC detection of an X-ray burst from the posion consistent with the globular cluster M15

Mikio Morii — Tue, 07 Jun 2011 12:21:49 +0000

MAXI/GSC detected an X-ray burst at the scan transit centered at UT 2011-06-05T00:10:03.
The burst was detected at least for 30 seconds within the 62 seconds triangular transit response of MAXI/GSC.
The nominal location of the source, assuming that the source flux was constant over the transit
(which probably was not), is determined as

(R.A., Dec) = (+322.76 deg, +12.03 deg)

= (21 31 3, +12 01 44)(J2000)

with a rectangular 90% statistical error box with the following corners:

(R.A., Dec) = (+322.65 deg, +12.24 deg)

= (21 30 35, +12 14 7)(J2000)
(R.A., Dec) = (+322.93 deg, +12.19 deg)

= (21 31 42, +12 11 14)(J2000)
(R.A., Dec) = (+322.87 deg, +11.82 deg)

= (21 31 28, +11 49 28)(J2000)
(R.A., Dec) = (+322.59 deg, +11.87 deg)

= (21 30 21, +11 52 20)(J2000)

There is additional systematic uncertainty of 0.2 degree (90% containment radius).
This position is consistent with that of the globular cluster M15,
whose position is (R.A, Dec) = (322.49 deg, 12.17 deg).
The burst flux was 220 +-20 mCrab in the 4 – 10 keV band.
This burst is though to be the type I X-ray burst, because the softening of the spectrum was observed.
As reported in ATEL #3363, #3378, #3393, this source has been active recently.

MAXI data process has recovered.

Tatehiro Mihara — Wed, 30 Mar 2011 10:10:27 +0000

We have returned to the regular data process since March 25. The data between March 11-24 are to be filled succeedingly. In addition, we started a frequent update service in every 4 hours, first for 4U 1608-52 (ATel #3237) and Swift J164449.3+573451 (ATel #3244).

MAXI data stopped by the earthquake.

Tatehiro Mihara — Mon, 14 Mar 2011 05:03:09 +0000

The ISS-opration building in JAXA Tsukuba space center was damaged by the earthquake on March 11, 2011. The building contains the computers which receive MAXI telemetry data from NASA and store them. The computers have stopped since then. MAXI data also stopped and we can not issue alerts. We think it will take more than a week for the recovery. The MAXI itself in orbit has no problem and continues the observation. The data will be sent to Tsukuba space center afterwards.

Be X-ray binary pulsar A0535+262 started a new giant outburst.

Tatehiro Mihara — Wed, 23 Feb 2011 07:46:18 +0000

MAXI/GSC has detected a new outburst from Be transient X-ray binary pulsar A0535+262 (Atel #3166). The figure shows the lightcurve folded with 110.2-day orbital period (Moritani 2010) in the 1.5 yr MAXI observations. Orbital phase zero corresponds to the periastron. The current light curve (orange) traces the previous giant outburst (blue) in December 2009 very well. (It may be a little smaller this time). The He I double line indicates a new gas-disk ejection from the Be star (Atel #3176). No strong precursor before MJD55601 (= Feb 9) may indicate that the gas was ejected very recently just before the “He I double line” observation (Feb 5). The short (1.2 yr) recurrent time shows that the Be star has become active.

MAXI/GSC detects a new activity from binary X-ray pulsar GX 304-1

Motoki Nakajima — Fri, 10 Dec 2010 00:52:23 +0000

MAXI/GSC detected a new activity from transient pulsar GX 304-1. The figure shows the lightcurve folded with 132.5-day orbital period. As shown in below figure, the current flux increase is about 1-week earlier than that of the previous outburst within the orbital cycle of 132.5-day period. Thus, the current activity may be a precursor, or an onset of an anomalous giant outburst that occurs out of regular recurrent phase. We have reported this news to Astronomer’s Telegram #3075.

MAXI alert status in October 2010

Mitsuhiro Kohama — Sun, 31 Oct 2010 14:29:09 +0000

MAXI team reported three detections of the transient events to Astronomer’s Telegram (ATEL) in October, 2010.

2990: Short X-ray Transient Detection by MAXI/GSC Tomida 2010 Oct 31 9:49
2970: MAXI/GSC detects a new activity from Be pulsar A0535+262 Mihara, 2010 Oct 25 21:33
2959: MAXI/GSC detects an X-ray transient MAXI J1409-619 Yamaoka, 2010 Oct 20 11:06

Daily Spectra for ten sources are open.

Tatehiro Mihara — Thu, 28 Oct 2010 08:37:26 +0000

We open daily spectra of ten bright sources today. There is a spectrum plot following light curves and images for each source page. The spectrum is fitted with wabs * power-law model and the parameters are written in the plot. One can download the spectrum, background and response files by clicking “Download spectrum, background and response” below the plot. After extracting the tar.gz file, one can fit the spectrum with your XSPEC software. The sources whose spectrum is available are Crab, Sco X-1, Cen X-3, Her X-1, GX 9+9, GX 9+1, GX 13+1, GX 17+2, GRS 1915+105, and Cyg X-2.

The daily spectrum of Crab, which is available at http://maxi.riken.jp/top/index.php?cid=1&jname=J0534+220

MAXI/GSC detects a new activity from X-ray pulsar A0535+262

Motoki Nakajima — Tue, 26 Oct 2010 02:49:36 +0000

We reported in Atel#2970 (Mihara et al.) that MAXI/GSC detected a new activity from X-ray pulsar A0535+262. The figure shows the recent four light curves folded with 115-day outburst period. The current consecutive activities exhibit the outbursts and precursor events at phases ~0.2 and ~0.95, respectively. The phase zero is taken at MJD 55153.5, which is the periastron passage prior to the previous giant outburst.